Investigating when we should swap versions

etcd-manager/pkg/etcd/etcdserver.go

@@ -88,7 +88,7 @@ func NewEtcdServer(baseDir string, clusterName string, listenAddress string, lis
 	}
 
 	// Make sure we have read state from disk before serving
-	if err := s.initState(); err != nil {
+	if err := s.initStateOnStartup(); err != nil {
 		return nil, err
 	}
 
@@ -118,7 +118,11 @@ func (s *EtcdServer) Run(ctx context.Context) {
 	})
 }
 
-func readState(baseDir string) (*protoetcd.EtcdState, error) {
+// readState loads the saved state from the directory.
+// If no state is found, returns (nil, nil).
+// If replaceEtcdVersion is true, we will "bump" old etcd patch versions to a supported version.
+// replaceEtcdVersion means we don't need to have every etcd version available.
+func readState(baseDir string, replaceEtcdVersion bool) (*protoetcd.EtcdState, error) {
 	p := filepath.Join(baseDir, "state")
 	b, err := os.ReadFile(p)
 	if err != nil {
@@ -134,6 +138,16 @@ func readState(baseDir string) (*protoetcd.EtcdState, error) {
 		return nil, fmt.Errorf("error parsing state file: %v", err)
 	}
 
+	// Maybe use the recommended etcd version
+	if replaceEtcdVersion && state.EtcdVersion != "" {
+		etcdVersion := state.EtcdVersion
+		startWith := etcdversions.EtcdVersionForAdoption(etcdVersion)
+		if startWith != "" && startWith != etcdVersion {
+			klog.Warningf("starting server from etcd %q, will start with %q", etcdVersion, startWith)
+			state.EtcdVersion = startWith
+		}
+	}
+
 	return state, nil
 }
 
@@ -151,12 +165,16 @@ func writeState(baseDir string, state *protoetcd.EtcdState) error {
 	return nil
 }
 
-func (s *EtcdServer) initState() error {
+// initStateOnStartup populates the state from local disk.
+// It should only be called on initial startup; after that
+// we are under control of the leader.
+func (s *EtcdServer) initStateOnStartup() error {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
 	if s.state == nil {
-		state, err := readState(s.baseDir)
+		replaceEtcdVersion := true
+		state, err := readState(s.baseDir, replaceEtcdVersion)
 		if err != nil {
 			return err
 		}
@@ -170,7 +188,7 @@ func (s *EtcdServer) initState() error {
 }
 
 func (s *EtcdServer) runOnce() error {
-	if err := s.initState(); err != nil {
+	if err := s.initStateOnStartup(); err != nil {
 		return err
 	}
 
@@ -330,6 +348,7 @@ func (s *EtcdServer) JoinCluster(ctx context.Context, request *protoetcd.JoinClu
 			Nodes:        request.Nodes,
 		}
 		s.state.Quarantined = true
+
 		s.state.EtcdVersion = request.EtcdVersion
 
 		if err := writeState(s.baseDir, s.state); err != nil {
@@ -605,18 +624,9 @@ func (s *EtcdServer) startEtcdProcess(state *protoetcd.EtcdState) error {
 		return err
 	}
 
-	etcdVersion := state.EtcdVersion
-	// Use the recommended etcd version
-	{
-		startWith := etcdversions.EtcdVersionForAdoption(etcdVersion)
-		if startWith != "" && startWith != etcdVersion {
-			klog.Warningf("starting server from etcd %q, will start with %q", etcdVersion, startWith)
-			etcdVersion = startWith
-		}
-	}
-	p.EtcdVersion = etcdVersion
+	p.EtcdVersion = state.EtcdVersion
 
-	binDir, err := BindirForEtcdVersion(etcdVersion, "etcd")
+	binDir, err := BindirForEtcdVersion(p.EtcdVersion, "etcd")
 	if err != nil {
 		return err
 	}